Add size regex for used RAM

This was previously omitted, causing arduino-builder to not report the
amount of RAM used. This adds the regex, based on the regex used by AVR
(omitting the .noinit section, which is not supported by the SAMD linker
scripts).

Author: matthijskooijman

platform.txt

@@ -118,6 +118,7 @@ recipe.output.save_file={build.project_name}.{build.variant}.{build.preferred_ou
 ## Compute size
 recipe.size.pattern="{compiler.path}{compiler.size.cmd}" -A "{build.path}/{build.project_name}.elf"
 recipe.size.regex=^(?:\.text|\.data|)\s+([0-9]+).*
+recipe.size.regex.data=^(?:\.data|\.bss)\s+([0-9]+).*
 
 # Upload/Debug tools
 # ------------------